Results from long-period MT array in the Newer Volcanic Province, Western Victoria, Australia

Abstract

The Newer Volcanic Province (NVP), western Victoria, Australia, represents the most extensive and youngest volcanism of the entire intraplate volcanic field of eastern Australia. The nature of, and mechanism(s) for, melting of the source magma of the NVP is still unclear. Previous teleseismic studies associate the magma genesis for the NVP to conduits of a mantle plume. Here we present data from a long-period MT array conducted over the same grid as the teleseismic survey, across the southern end of the Lachlan and the Delamerian Orogenies, western Victoria in a rectangular grid with nominal 270 km x 150 km dimensions. Forward modelling of MT data suggests that the lithosphere beneath the Lachlan orogeny is more conductive than the Delamerian counterpart by several orders of magnitude, perhaps associated with thinning of the lithosphere beneath the Lachlan orogeny. The phase tensor analysis illustrates that there is an increasing conductivity trend beneath the Central Highlands, observed up to 500s, that is perhaps associated with NVP magma source region. Furthermore, the geoelectric strike direction beneath the Central Highlands is aligned parallel to the NW-SE Mesozoic-Cenozoic fracture zones, which coincides with the highest density of eruptions of the volcano field.